Saturday, May 21

Covid-19. Fourth dose: Israel dampens hopes on the effectiveness of the vaccine against Omicron

At the very beginning of January, the French CEO of the American pharmaceutical group Moderna, Stéphane Bancel, could not imagine any other solution: “I still believe that we will need reminders in the fall of 2022 and beyond”, he said. he declared on January 6th.

Hopes showered with a fourth dose

According to him, the effects of the booster dose would diminish over time, which would necessitate the injection of a new booster dose.

The same day, Prime Minister Jean Castex announced that the government would open the possibility of using it when the health authorities have given their approval.

Israel has already started to inject this famous fourth dose to some of its inhabitants – only the most fragile: it is not necessarily recommended for the whole population.

An Israeli hospital conducted “the first study of its kind in the world”, and the results are much less exciting than expected.

Or even… lapidary:

The effectiveness of the fourth injection against the Omicron strain is low

Sheba Hospital, near Tel Aviv, on Monday

Since the start of the vaccination campaign at the end of December 2020, Israel has been a life-size laboratory on the effectiveness of vaccines against Covid-19, observed by other countries which started their campaigns a little later and a little slower. respective.

Transmission remains high, even with four doses

Also faced with the threat of the Omicron variant, the Jewish state decided in mid-December to conduct a study entrusted to the Sheba Medical Center, “to examine the effects of a fourth so-called ‘booster’ injection on the level of antibodies in 200 volunteers (finally 274, editor’s note)”.

The study first examined over a week – the trial must last at least six months – to what extent antibodies increase after this injection of Pfizer or Moderna (154 candidates with Pfizer, 120 with Moderna), compared to a control group that did not receive a fourth dose.

According to the first results “the antibodies [des candidats] increased five-fold, indicating that the vaccine is working and providing protection against serious complications,” the hospital said.

But this Monday, three weeks after the start of clinical trials, Professor Gili Regev-Yochay, who is leading this study, made an important clarification: this fourth dose “offers only partial defense against the virus”.

Pfizer and Moderna vaccines, which were more effective against other variants, offer less protection against Omicron

Pr Gili Regev-Yochay, who leads the study

Most severe forms still avoided

In short: as with the previous doses, a relatively recent injection increases the level of antibodies and therefore increases protection – especially against severe forms. But regardless of the number of doses, messenger RNA vaccines from Pfizer and Moderna are not very effective in curbing infections.

Even when the level of antibodies decreases, it seems that its vaccines effectively prevent, over time, most of the severe forms… without the administration

The first feedback from Israel is not very encouraging for advocating the fourth dose of vaccine

Antoine Flahault, epidemiologist

And to remember that we must also consider or not this booster dose according to other criteria:

The fourth dose is highly debated scientifically at the moment, including in Israel, especially for reasons of acceptability. The population was much more reluctant there than for the third dose

A helpful reminder for at-risk populations

Regarding the fourth injection, Israel prioritized, in December, the immunocompromised then the elderly over 60 and caregivers.

In total, more than 537,000 Israelis have currently received the booster, according to the latest data from the Health Ministry. A reminder that remains effective for these specific audiences:

Although the vaccine we have today does not offer optimal protection against infection with the Omicron strain, it is correct to continue the vaccination campaign for populations at risk.

Pr Gili Regev-Yochay

On the other hand, multiplying the reminders of vaccines designed from the initial so-called Wuhan strain does not seem to be the ideal solution:

“We expect two things from a vaccine: humoral efficacy and cell-mediated efficacy,” recalls Antoine Flahault. “The first concerns the level of antibodies, the first dam of protection for the vaccine. The latter, even if it is effective, is not very convincing today vis-à-vis new variants (Omicron and its strong immune escape, editor’s note) and we can probably not expect that the fourth dose is a big game-changer. As for cell-mediated efficacy – against severe forms of the disease – there the vaccines seem to confer quite relevant immunity”, insists the epidemiologist.

Long-awaited new vaccines

In this context, several pharmaceutical groups are working on a new version of the anti-Covid-19 vaccine which this time would be more effective against the Omicron variant.

At the beginning of December, Pfizer and BioNTech announced this new vaccine “by March in case adaptation is necessary to increase the level and duration of protection”.

At the end of December, Moderna aimed to bring its new vaccine to market “in the second quarter, around the summer” of 2022.

It is very good that the laboratories work on these questions, but we must not lose sight of the fact that the decisions must be taken by independent public bodies, for example the WHO and its expert committees.

Antoine Flahault, on France 24

Which wishes to put the UN organization back at the center of decisions, as is done for the flu vaccine: “The composition of the flu vaccine is decided each year at a WHO meeting – in February for the Northern Hemisphere, in September for the Southern Hemisphere – then recommended for all vaccine manufacturers on the planet. Perhaps one day the UN organization will recommend the composition of a vaccine against a coronavirus, but we are not there yet. »

Reference-www.leprogres.fr

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